The overwhelming majority of the public relies on the manual toothbrush as the primary tool for removal of dental plaque and hence the prevention of the most common oral diseases (caries, gingivitis and periodontitis). However, there are two major obstacles to the efficacy of a manual toothbrush: (1) patient compliance in using a manual brush twice daily for a sufficient period of time (at least 2 minutes) to effectively remove plaque; and (2) inadequate plaque removal, as it only occurs on tooth surfaces directly contacted by the bristles. Power brushes, used by 30% of Americans, offer the potential for better oral health, because their rapid bristle motion can more effectively remove plaque within the reach of the bristles and weak fluid forces created by bristle motion may remove some of the plaque that is beyond the direct reach of their bristles. However, even the best power brushes require a minimum 2-minute brushing to achieve optimal results (while leaving significant interproximal and subgingival plaque). Therefore, the development of a power toothbrush capable of removing the majority of plaque both within reach of and beyond the reach of the bristles over a shorter brushing time (e.g. 1 minute) could provide a significant advance in oral health -which is the goal of this multi-phase SBIR project. Phase I results indicated the feasibility of a power toothbrush that incorporates a novel combination of sonic and ultrasound physical processes to rapidly and safely remove plaque at levels well beyond the capabilities of existing power toothbrushes. Phase I results were obtained with a suitably altered power toothbrush that has clear manufacturing potential. The purpose of the substantial Phase II work proposed here is to 1) finalize the choice of sonic and ultrasound conditions for optimal dental plaque removal and safety via in vitro assays, 2) optimize the design of the proposed toothbrush for acoustic efficiency, reliability and durability, and 3) investigate efficacy and safety of a finalized toothbrush in human clinical studies. The development of a power toothbrush capable of removing the majority of plaque both within reach of and beyond the reach of the bristles within a short period of brushing time would mark a significant advance in oral health. Success in Phase II will set the stage for a Phase III commercialization effort during which Second Act Partners will continue the pursuit of its business plan and will raise the private-sector capital required to begin manufacturing and marketing. This novel product will address a power toothbrush market that is currently over $1 billion in the US and over $2 billion worldwide - one that is growing at 11% per year. [unreadable] [unreadable] [unreadable]